In recent years, as a nonvolatile storage medium for storing information, a NAND flash memory is utilized in an information storage apparatus such as an SSD (Solid State Drive). The NAND flash memory is integrated as a semiconductor chip to have a capacity of several tens [Mbytes]. The SSD includes such semiconductor chips in plurality to realize a total capacity of several hundred [Mbytes]. Besides, the write of information into or the erase of information from the NAND flash memory is controlled in units of a predetermined capacity.
In the information storage apparatus, encrypted information is stored in the storage medium, and the encryption information read out from the storage medium is decrypted. Identical key information is utilized in the encryption and decryption of the information, whereby the decryption of the encrypted information is permitted. In the SSD, plural interface ICs for transmitting and receiving information to and from the plural semiconductor chips are included in correspondence with these semiconductor chips being the storage medium. The respective interface ICs concurrently execute the encryptions or decryptions of information for the corresponding semiconductor chips, by utilizing appropriate key information.
That is, in the SSD, the plural key information are sometimes utilized concurrently by the plural interface ICs which execute the encryptions or decryptions of the information. Besides, in an encryption system including plural encryption processing blocks, the plural encryption processing blocks store key information for encryptions and decryptions, respectively and individually.
Thus, even in a case where common key information is utilized for encryption and decryption, plural blocks which execute encryption processing store key information respectively and individually. As a result, the key information for the encryptions and decryptions of information are not stored efficiently.